Is everyone on Less Wrong an atheist?
It certainly can seem that way at times! Religion tends to get heavily criticised around here, as many atheists see it as a major source of irrationality. There are a few religious members, however, and by no means is being an atheist a prerequisite to being a part of our group. As long as you’re interested in honing your beliefs to match the truth (whatever it may be), you’re welcome here.

As one of the religious folk on LW, if your goal is to get people to still show up, I might tweak it to:

LW is definitely disproportionately atheist, but there are some religious members. We're interested in honing our beliefs to match the truth (whatever that may be) and a lot of our members have concluded religion is false and is a major source of irrationality. The existence of god(s) isn't the only claim about the world we discuss, and our focus isn't just on settling one claim but getting better at making sense of the evidence to deal with all sorts of claims. If that's a project you're interested in, you're very welcome at our meetings.

That way the focus is on method not on "we spend a lot of time heavily criticizing religion"